A very informative and important document to understand the lucene scoring. Generaly it takes very much time to dig this up :( . Copying here for the same reason. Apache Lucene - Scoring Introduction Scoring Fields and Documents Score Boosting Understanding the Scoring Formula The Big Picture Query Classes Changing Similarity Changing your Scoring -- Expert Level Appendix Algorithm Introduction Lucene scoring is the heart of why we all love Lucene. It is blazingly fast and it hides almost all of the complexity from the user. In a nutshell, it works. At least, that is, until it doesn't work, or doesn't work as one would expect it to work. Then we are left digging into Lucene internals or asking for help on java-user@lucene.apache.org to figure out why a document with five of our query terms scores lower than a different document with only one of the query terms. While this document won't answer your specific scoring issues, it will, hopefully,...